From Event: SPIE Optical Engineering + Applications, 2016
X-ray targets in microfocus x-ray tubes fail primarily due to sublimation and evaporation of tungsten while exposed to
the electron beam. The temperature at the point of impact of the electron beam depends on the beam energy (200-300
kV), the beam current (<10 mA), the cross section (<1 mm) and the intensity profile. In order to preserve the target for a
reasonable lifetime, temperatures at the spot do not typically exceed 2500 C. As tungsten evaporates from the surface of
the target, the surface starts to pit and this can affect the x-ray production in multiple ways: the photon flux decreases,
the heel effect is enhanced, the effective spot size changes shape and/or size. Indirectly, the target damage incurred over
time or due to intense use will undermine the image quality by reducing image contrast, changing the resolution or
degrading the signal to noise ratio. A detailed description of how x-ray target damage is incurred and the potential
impact on image quality is reviewed in detail. Experimental results showing the target damage and associated loss of
image quality are discussed.
Vance S. Robinson, Thomas Raber, and William R. Ross, "Image-based characterization of microfocus x-ray target failure," Proc. SPIE 9964, Advances in Laboratory-based X-Ray Sources, Optics, and Applications V, 996405 (Presented at SPIE Optical Engineering + Applications: August 30, 2016; Published: 16 September 2016); https://doi.org/10.1117/12.2238968.
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